115-W Tm:YAG diode-pumped solid-state laser

A compact diode-pumped Tm:YAG laser capable of generating greater than 100 W of CW power at 2 μm has been demonstrated. A scalable diode end-pumping architecture is used in which 805-nm radiation, coupled to the wing of the Tm³⁺³H₆-³H ₄ absorption feature, is delivered to the end of the laser rod via a lens duct. To facilitate thermal management, undoped YAG end caps are diffusion bonded to the central doped portion of the laser rod. For 2% and 4% Tm-doped rods of the same length, the lower doping level results in higher power, indicating that cross relaxation is still efficient while offering lower thermal stress and reduced absorption at the laser wavelength. Output powers for various output coupler reflectivities are compared to the predictions of a quasi-three-level model. Thermal lensing, cavity stability, and stress-induced birefringence measurements are described. The beam quality was analyzed with the 2% Tm-doped rod and a flat output coupler, yielding M² values of 14-23     

Diode-pumped ytterbium-doped Sr5(PO4)3F laser performance

The performance of the first diode-pumped Yb³⁺-doped Sr ₅(PO₄)₃F (Yb:S-FAP) solid-state laser is discussed. An InGaAs diode array has been fabricated that has suitable specifications for pumping a 3×3×30 mm Yb:S-FAP rod. The saturation fluence for diode pumping was deduced to be 5.5 J/cm ² for the particular 2.8 kW peak power diode array utilized in our studies. This is 2.5× higher than the intrinsic 2.2 J/cm ² saturation fluence as is attributed to the 6.5 nm bandwidth of our diode pump array. The small signal gain is consistent with the previously measured emission cross section of 6.0×10^-20 cm², obtained from a narrowband-laser pumped gain experiment. Up to 1.7 J/cm³ of stored energy density was achieved in a 6×6×44 mm Yb:S-FAP amplifier rod. In a free running configuration, diode-pumped slope efficiencies up to 43% (laser output energy/absorbed pump energy) were observed with output energies up to ~0.5 J per 1 ms pulse. When the rod was mounted in a copper block for cooling, 13 W of average power was produced with power supply limited operation at 70 Hz with 500 μs pulses     

Goodness of visual regularities: A nontransformational approach.

Until recently, the transformational approach provided the only available formal analysis of visual regularities like repetition and mirror symmetry. This theoretical study presents a new analysis, based on the recently developed concept of holographic regularity. This concept applies to the intrinsic character of regularity and specifies the unique formal status of perceptually relevant regularities. The crucial point is that the two analyses imply the same structure for repetition but a different structure for mirror symmetry. Transformationally, mirror symmetry is an all-or-nothing property, whereas holographically, it is a graded property. This difference pervades the understanding of both perfect regularities and perturbed regularities. Whereas the transformational approach explains hardly any goodness phenomenon, the holographic approach explains a wide variety of goodness phenomena in a coherent way that is ecologically plausible as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the definition of power factor and apparent power in unbalancedpolyphase circuits with sinusoidal voltage and currents

Definition for the apparent power S and for the power factor PF in unbalanced polyphase circuits with sinusoidal waveforms are presented. It is proved that the definition S²=(V_a²+V _b²+V_c²) (I _a²+I_b²+I _c²) has a definite physical meaning, leading itself to a convenient resolution in positive, negative and zero sequence, nonactive and active power. It is suggested that the power factor be represented with the help of the ratio P⁺/ S, where P⁺ is the positive sequence active powers     

Robotic nucleic acid isolation using a magnetic bead resin and an automated liquid handler for biological agent simulants

The events that occurred following the mailing of Bacillus anthracis-laced envelopes through the postal system has highlighted the need to perform biological screening on large numbers of environmental samples. High-throughput screening that relies on integrated robotic systems to speed analysis has been undertaken to handle the surge in samples requiring testing in events involving weapons of mass destruction. These automated screening systems require DNA extraction methods capable of handling environmental samples that contain inhibitors and have target organisms at low concentrations. This study describes the development of a method for the detection of the biological warfare agent simulants Erwinia herbicola and Bacillus subtilis var. niger spores using paramagnetic bead-based resin with an automated liquid handler and environmental samples.     

Chronopotentiometric potential-time curves of electron transfer across the interface between two immiscible electrolyte solutions

Theoretical potential-time curves were derived that are mathematical expressions of the electron transfer reaction O1 (w) + R2(non) ? R1(w) + O2(non) proceeding at the interface of two immiscible phases between the redox couple O1/R1 in the aqueous phase (w) and the redox couple O2/R2 in the non-aqueous phase (non) under galvanostatic conditions. Procedures for the determination of the diffusion coefficients of the reactants in the corresponding phase and for the evaluation of thermodynamic and kinetic parameters of the electron transfer reaction from the potential-time curves were suggested.     

STUDY OF EXTRACTION METHODS FOR HIGH-ASH COAL USING LOW-BOILING EXTRACTING AGENTS. 2.MECHANICAL STIRRING METHODS

The quality, as well as the quantity of coal-derived liquids are Investigated using low-boiling extracting agents and mechanical stirring. A broad range of solvents with different boiling point and polarities are studied in order to generate the desired coal-derived material. Several experimental conditions are shown to be critical: the nature of solvent, solvent-to- coal ratio and the volume of washing solvent. The method is shown to be reliable for generating coal-derived products, since it is performed under mild experimental conditions and generates amounts of material comparable to Soxhlet extraction procedures in much less time. In addition, it is cheap, easy to perform, fast and reproducible.     

Optimum Shunt Capacitor for Power Factor Correction at Busses with Lightly Distorted Voltage

The goal of this paper is to determine the effect of time variation of system impedances and voltage harmonics on the value of optimum capacitor for power factor correction at busses with nonsinusoidal voltage. Two types of 24 hours time-variation of voltage harmonices and Thevenin impedance are assumed. The equivalent load impedance is also considered time variable and assumed to contain a large proportion of induction motors. The daily energy losses are computed and graphed in function of the shunt capacitance used for power factor correction. The results of this study indicate that in order to avoid resonances and to find the optimum capacitor the time variation of harmonics and system impedances must be known as precise as possible.     

Energetical factors in power systems with nonlinear loads

Contents The classical definitions for the energetical determining factors in power systems are reviewed and a new model for the apparent power is suggested. — Based on the volt-ampere characteristic of the nonlinear load, an equivalent circuit, containing linear elements, can be determined. In this way, load-flow and harmonic compensation studies can be simplified.

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Übersicht In der Arbeit werden zunächst die klassischen Definitionen erörtert; darauf basierend wird ein neues Modell für die Scheinleistung vorgeschlagen, das zu einer Ersatzschaltung mit linearen Elementen führt. Damit lassen sich z. B. Lastflußberechnungen und Kompensationsstudien vereinfachen.